Valve operated variable reactor



4/bodiment of the Patented Mar. 2, 1943 UNITED STATES PATENT Y,orrlcE vALvE orERA'rED VARIABLE REAc'roR Luis Charles Stenning, Park Hill, Ealing, England, assignor to The General Electric Company Limited, London, England 'Application September 6, 1941, Serial No.

In Great above specied are special' cases of the generalised ycircuit arrangement shown in Figure 1. Here VA and B are each a fourterminal network, having input terminals I, 2 and output ter- .'minals 3, 4; the networks are connected by connecting theircorrresponding terminals each to each; the combination is used as a two-terminal network (winch is the variable reactor) by applying to of a determinate frequency.- Y,

An object of this invention is to provide an improved form of variable reactor of the general type shown in Figure 1.

Referring to Figure 1, let 711, 721, 722 be the input,` transfer, and output admittance of A when connected to B. Let B be,"or be equivalent to, a potentiometer of ratio P across the terminals I, 2 feeding a valve with mutual conductance gm, whose output feeds a transformer of step-down ratio o. Then it is known that, it y is the admittance of the variable reactor,

real, either P or p 'ym/'yar must be imaginary but not both.

. with reference to the terminals I, 2 an oscillating current Y dotted rectangle 4 y The dotted rectangle 5 represents the four-terin the said Figure 1, but in? cludes also the transformer which is eiective- Britain September 30, 1940 3 Claims. '(ClI-178-44) The invention of example one embodiment of the invention. Y

In Figure 2, Li is an inductor across which the oscillating voltage V of frequency p/Zn is applied. It will usually bepart of a parallel tuned circuit of natural frequencyV near p/21r, and be in parallel with a condenser C1. 'I'he potentiometer P enclosed in the dotted rectangle I, consists of condensers C3 and C4 in series; Crwill often be'the valve hereafter-mentioned.

The ratio P is C4/(C;+C4)f. The capacity of t-hisl be added to that of C1 in The'voltage across C4 is applied to the input of Va valve 2 provided lwith means 3 for varying the grid bias and thereby the mutual conductance of the valve. Elementsi.l and 3 enclosed in represent gm in Figure 1.

minal network A ly present, according to well known principles, in

band-pass the contents of rectangle 5. addition to L1, are the inductor le, condenser-C2, and resistor Re in parallel, tuned to the frequency p/21r. If the valve 2 has appreciable output ad- According to this invention, in a variable. re-

actor of the type specified operating on the principle hereinbefore described with reference to Figure 1, the said potentiometer ratio P is substantially real, and the s aid ratio ym/722 is approximately a pure' imaginary. Preferably the ratio is imaginary owing to the presence in the path through the four-terminal network A of a. coupling by means of mutual inductance or capacity.

mittance, this is included in R2. ductance of Li and L2 is M.

Then, according to known principles, at the frequency 1'1/21.-

The mutual inthe mutual inductance M of Figure 2 is replaced by a condenser of capacity C5 connecting they upper will now be explained furtherV Figure 2, which shows by way Y `lter constituted by These contents, inr

In the modication shown in Figure 3, theV output terminals each to each and serving as a two-terminal network when an oscillating volti age of a determinate frequency is applied across said input terminals, said first four-terminal network being constituted by a step-down transformer comprising'a primary inductor and a secondary inductor coupled together and each being tuned by a capacity connected in shunt to resonate at the frequency of theapplied oscillating voltage, said second four-terminal network comprisngv a .potentiometer connected across the input. terminals thereof, a thermionic valve, and means for varying the mutual Yconductance of said valve, the input and output terminals of said valve being connected with respectively a tap on the said potentiometer and an'output terminal of the said networks, and the arrange-a ment being such that the product of the stepdown ratio of said transformer and the ratio of the transfer admittance to the output admittance of said first network, when so connected minal network being constituted by a step-down transformer comprising a primary inductor and a secondary inductor coupled together by means of mutual inductance, said second four-terminal network comprising a pOtentiometer consisting of two condensers` connected in series across the' input terminals thereof, a thermionic valve, and

means for varying the mutual conductance of said valve, the input and output terminals' of saidrvalve being connected with respectively a tap on the said potentiometer and an output terminal of the said networks, and the arrangement being such that the product of the stepdown ratio of said transformer and the ratio of the transfer admittance to the output admittance of'said first network, when so connected to said second network, is approximately a pure imaginary quantity.

to said second network, is approximately a Apure n i imaginary quantity. Y

2.A variable reactor of the type comprising an impedance element` and a thermionic valve connected thereto and means for varying the mutual conductance of' said valve, in which the effective value ofthe reactance of said element is Yvaried by adjusting the mutual conductance ofv said' valve, said reactor Ahaving a Yfirst and a second four-terminal network connected together'by connecting their correspondingrinput and output terminals each to'each and serving as ar two-terminal network when an oscillating voltage of a determinate frequency is applied across said input terminals,` said first four-ter- 3. A variable reactor of the type comprising an impedance element and a thermionic valve connectedv thereto and means for varying the mutual conductance of said valve, in which the effective value of the reactance of said element is varied by adjusting the mutualconductance of said valve, said reactor having a first and a'secnd four-terminal' network connected together: by connecting their corresponding input and output terminals each to each and serving as a two-terminal network when an oscillating voltage of a. determinate frequency is applied across 'said' input terminals, said first four-terminal network being constituted by a step-down transformer comprising a. primary inductor and a secondary inductor coupled together by means of a condenser, said second four-terminal network comprising a potentiometer consisting'of two condensers connected in series4 across the input terminals thereof, a thermionicvalve, and means for varying the mutual conductance of saidV valve, the input-andv output terminals of said valve being connected with respectively a tap on the said potentiometer and an output terminal of the said'networks, and thearrangement being su'ch that the product of the stepdown ratio of said transformer andv theratio of the transfer admittance to the output admittance of said first network, When so connected to said second network, is approximately a pure imaginary quantity. 1 

